So GARDINER. [Vol. XV. 



of the breeding season. The right half of the diagram shows 

 the same parts when the ova are rapidly approaching maturity. 

 The ova (p) which are destined for fertilization are contained 

 within the vitellarian portion of the oviduct {vt). These are 

 all about the same size and appear equally sure of surviving, 

 for all the ova in this gland are laid at the same time. Extend- 

 ing forward and at the same time upward from this vitellarium 

 is the ovary. 



With but slight magnification three distinct stages in the 

 breeding season may be distinguished among individuals. 

 Those approaching the breeding season have enlarged vitel- 

 laria which do not contain ova ; later the vitellaria are crowded 

 with enlarging ova, and again later, after the ova are deposited, 

 the vitellaria are completely collapsed. I have kept animals 

 for several weeks after they have laid to determine whether or 

 not they laid a second time during the same season, but have 

 found no evidence that they do so. The vitellarium did not 

 recover from its collapsed state. 



Double staining with lithio-carmine, followed by Lyons blue, 

 after a method described by Miss Katharine Foot (ii), shows 

 that the substance of the vitellarium is very different from that 

 of the ovarian ovum. In the latter, both nuclei and cyto- 

 plasm take the red stain with great avidity, but do not stain at 

 all with the Lyons blue. On the other hand, the greater part 

 of the vitellarium is indifferent to the lithio-carmine, but does 

 stain with the blue. Sections through the vitellarium (PI. IX, 

 Fig. 3) show it to be composed of large cells, the nuclei of which 

 are closely pressed against the cell walls. The nuclei, cell walls, 

 and a few fine protoplasmic filaments within the cell stain red, 

 while the cell contents stain a strong blue. Fig. 2 shows a sec- 

 tion through a portion of the vitellarium with three ova imbedded 

 in it. The ova have evidently just passed in from the ovary, for 

 they do not take the blue stain. Fig. 4 shows an ovum which 

 is about mature, having absorbed the dotter material from the 

 surrounding gland cells to such an extent that the red staining 

 cytoplasm, of which it was composed when it first entered the 

 vitellarium, is completely obscured. Around it are the col- 

 lapsed and empty gland cells. 



